This project involves several avenues of approach to a central problem, that of elucidating the contractile mechanism of smooth muscle, especially that of the female reproductive system. Mechanical interventions, consisting of small sinusoidal oscillations and large controlled stretches, are to be applied to isotonically and isometrically contracting smooth muscle strips (Rabbit mesotubarium superius and ovarian ligament). The results from the mechanical perturbations are to be analyzed in light of hypothesized contractile mechanisms. Similar muscle preparations are to be treated with non-ionic detergents in order to render their cell membranes permeable to ions (e.g., Ca ion; Mg ion) and molecules (e.g., ATP). Using these preparations, the cellular controlling and regulating functions of the above chemical species will be investigated and the resulting contractile behavior will be analyzed by the mechanical methods mentioned above. Electron microscopic examination of muscle strips fixed at various lengths and contractile states will be used to assess the arrangement (and changes therein) of thick myofilament array for the purpose of deducing a plausible geometrical model for the contractile apparatus, a model which must also be consistent with the results of the proposed mechanical experiments.